1. Field of Invention
This invention relates to the formation of elastomeric pipe linings, and specifically relates to the formation of elastomeric flange linings for the flanges of such pipes.
2. Statement of the Art
Metal pipe and valve fittings are widely used in many industries as conduits for fluid materials, including liquids and gases. In some industries, such as mining, paper and pulp, and wastewater treatment, fluids containing abrasive solids or corrosive chemicals are transported through vast systems of piping. Because the abrasive solids or corrosive chemicals can damage and deteriorate the inner surface of metal pipes and valves, the pipe and valves are lined with elastomeric materials which are highly resistant to chemical or abrasive corrosion, thereby protecting the inner surface and integrity of the pipe and valve fittings. The technology for lining such pipes and valves is well know.
Lined pipe and valves are typically joined end-to-end to form extensive fluid transport pathways. An inherent problem occurs at the joining of pipe and valves, however, in that the pipe linings of adjacently and co-axially joined pipes must seat tightly against each other and within very small tolerances or the fluid flowing through the pipes will wear on the lining and will seep through the space left between the adjacent linings. Failure of the lining then occurs. The lining will degrade and eventually the lining may delaminate or peel away from the inner surface of the metal pipe. Leakage at the pipe joint results.
In an effort to alleviate such problems, an elastomeric gasket may be positioned between the joined pipes. However, failure can occur in the area of the gasket for the same reasons stated with respect to joined pipe linings. That is, bulging of the elastomeric lining in proximity to the gasket, when the gasket is under compression, exposes the bulging lining to wear and degradation. Infiltration of fluid into any spaces left between the gasket and the adjoining pipe linings on either side of the gasket can lead to erosion and failure of the gasket.
Another means of sealing pipe joints at the adjoining linings has been to extend the elastomeric lining over the flanges at the ends of the pipes to act as a unitary gasket fitting. While an elastomeric flange lining provides a seal of greater integrity, a secondary problem occurs when the adjacent pipes are connected coaxially end-to-end. Specifically, the compression of one elastomeric flange lining against an adjacent elastomeric flange lining when the pipes are bolted together causes the elastomeric material to bulge inwardly toward the interior of the pipe. When abrasive materials or corrosive chemicals flowing through the pipe system encounter the bulge of elastomeric lining at the joining of two pipe linings, the bulge becomes worn and deteriorated, leading to failure of the lining.
Thus, it would be advantageous to provide elastomeric flange linings for pipes and valves which do not bulge inwardly toward the interior of the pipe under compression exerted on the flange linings when adjacent pipes are coaxially joined.